Doctoral Dissertation Research: Role of Transportation in Employment Outcomes of the Disadvantaged

负担得起的高效交通对于低收入个人的就业至关重要，因为他们可用于流动的资源较少。为了帮助改善弱势群体的就业结果，规划者和政策制定者强调了交通的重要性，并建议扩大公共交通服务或以较低的成本提供汽车。为了证明这些政策的合理性，许多研究人员研究了交通对弱势群体劳动力市场结果的影响。研究的重点是一个关键因素-处境不利的个人是否有充分的“机会”获得工作机会。因此，有一个基本假设，即无障碍和就业是直接相互关联的。也就是说，过去的研究是建立在这样的想法，即低收入的个人有可靠的交通选择或更容易获得工作机会的汽车或公共交通工具将选择一种特定的交通模式为工作相关的旅行。尽管这似乎是一个合乎逻辑的假设，但交通便利本身并不足以保证个人选择某种旅行方式。通过系统地考虑低收入者的出行方式选择决策，本论文的目的是阐明目前的理解之间的关系的可达性和就业的经济弱势群体。特别是，这个项目提出了两个研究问题。第一，决定低收入者出行方式选择的因素是什么？第二，在系统地考虑了出行方式选择之后，获得工作的机会是否仍然对改善贫困者的就业结果产生直接和独立的影响？本研究利用在旧金山弗朗西斯科和亚特兰大地区收集的家庭旅行调查数据，通过进行一系列统计分析来估计穷人的就业结果作为可达性和旅行方式选择的函数，从而解决了上述问题。调查人员希望证明模式选择决策的重要性，在检查低收入个人的就业结果的无障碍的影响。本论文的重要性体现在两个方面。首先，很少有研究在研究无障碍环境如何影响就业时系统地将穷人的旅行方式选择纳入其中;很少考虑到交通工具提供的高水平就业无障碍环境并不能保证个人会选择特定的旅行方式。因此，在文献中缺少的是无障碍环境如何影响穷人的出行方式选择，以及出行方式的决定如何影响就业。拟议的研究将填补文献中的这一空白。其次，本研究的结果将为未来的交通政策提供指导。目前针对穷人的交通政策往往侧重于通过提供汽车或扩大过境服务来改善无障碍环境。然而，如果这项研究发现，有具体到每个人的因素，限制他们的出行方式的选择，如果模式的选择确实有显着的就业影响，这项研究可以告知政策制定者的来源，这种限制的价值无障碍。然后，公共部门可以设计专门旨在消除这些制约因素的政策工具，从而确保从目前的促进无障碍战略中获得更高的社会回报。

Affordable and efficient transportation is crucial for the employment of low-income individuals, as they have fewer resources to spend on mobility. To help improve employment outcomes of the disadvantaged, planners and policy makers have emphasized the significance of transportation and suggested expanding public transit services or providing automobiles at lower cost. To justify such policy efforts, numerous researchers have studied the impact of transportation on labor market outcomes of the disadvantaged. The studies have focused on a key element -- whether or not disadvantaged individuals have adequate "accessibility" to reach job opportunities. Thus, there is a fundamental assumption that accessibility and employment are directly connected to each other. That is, the past research is built upon the idea that low-income individuals with reliable access to a transport option or higher accessibility to job opportunities by car or public transit will choose a particular transport mode for work-related travels. Despite this seemingly logical assumption, accessibility alone does not warrant an individual's choice of a certain travel mode. By systematically considering travel mode choice decisions of low-income individuals, the objective of this dissertation is to shed new light on the current understanding of the relationship between accessibility and employment of the economically disadvantaged. In particular, this project asks two research questions. First, what are the factors determining travel mode choices of low-income individuals? Second, after systematically considering travel mode choices, does accessibility to jobs still have a direct and independent impact on improving employment outcomes of the deprived? This research, using household travel survey data collected in the San Francisco and Atlanta regions, addresses the above questions by conducting a series of statistical analyses to estimate employment outcomes of the poor as a function of accessibility and travel mode choices. The investigators expect to demonstrate the significance of mode choice decisions in examining the impact of accessibility on the employment outcomes of low-income individuals. This dissertation is important in two respects. First, few research studies have systematically integrated travel mode choices of the poor in studying how accessibility affects employment; little consideration has been given to the idea that a high level of job accessibility provided by a transport means does not guarantee that individuals will choose the particular travel mode. Thus, what is missing in the literature is how accessibility affects travel mode choices for poor individuals, and how travel mode decisions subsequently influence employment. The proposed study will fill this gap in the literature. Second, the findings from this research will offer guidance for future transportation policy. Current transportation policies for the poor tend to focus on improving accessibility by providing cars or expanding transit services. However, if this study finds that there are factors specific to each individual that restrict their travel mode choices, and if mode choices indeed have significant impact on employment, this research can inform policy makers about the sources of such constraints that limit the value of accessibility. The public sector can then design policy instruments that are specifically aimed at removing such constraints, thus ensuring higher social returns from present accessibility-enhancing strategies.